The invention relates to an auto-injection device. Such auto-injection devices are used for the administration of products, in particular medically or cosmetically effective fluids. For administration, an injection needle through which the product is dispensed is automatically inserted into a tissue by a predetermined path length after having been triggered by a drive mechanism.
Auto-injection devices typically comprise a housing, a container shiftably or moveably accommodated by the housing from which a product to be administered is dispensed through a needle arranged at an outlet of the container by advancing a piston, and a driven member of a drive unit, the driven member being shiftably accommodated by the housing. During auto-injection, the driven member advances the container in relation to the housing in the forward direction to a predetermined frontal position for inserting the needle, and the driven member advances the piston within the container for dispensing the product. When the container has reached its frontal position during an auto-injection, the needle has been advanced by a predetermined path length with respect to the container. The path length may also determine the penetration depth of the needle.
Auto-injection devices of the described design are known from U.S. Pat. Nos. 5,514,097; 159,192; and 5,643,214; as well as European Patent No. 0 516 473 B1. In the known auto-injection devices, the container is advanced together with the attached needle by a pressure which the driven member exerts on the piston.